Polypharmacy, Potentially Inappropriate Medications, and Drug-to-Drug Interactions in Patients with Chronic Myeloproliferative Neoplasms

Polypharmacy, potentially inappropriate medications (PIMs), and drug-to-drug interactions (DDIs) are highly prevalent in the elderly and may have adverse effects on health-related outcomes. Their occurrence and clinical and prognostic associations in patients with chronic myeloproliferative neoplasms (MPN) are unknown. We retrospectively evaluated polypharmacy, PIMs, and DDIs in a cohort of 124 MPN patients (essential thrombocythemia, ET = 63, polycythemia vera, PV = 44, myelofibrosis = 9, MPN unclassifiable = 8) from a single community hematology practice. There were 761 drug prescriptions with a median of five prescribed medications per patient. Polypharmacy, at least one PIM (calculated for persons >60 years of age, n = 101), and at least one DDI were recorded in 76 (61.3%), 46 (45.5%), and 77 (62.1%) of patients, respectively. Seventy-four (59.6%) and twenty-one (16.9%) patients had at least one C or at least one D interaction, respectively. Among other associations, polypharmacy and DDIs were associated with older age, management of disease-related symptoms, osteoarthritis/osteoporosis, and different CV disorders. In multivariate analyses adjusted for clinically meaningful parameters, both polypharmacy and DDIs were significantly associated with inferior overall survival (OS) and time to thrombosis (TTT), whereas PIMs had no significant associations with neither OS nor TTT. There were no associations with bleeding or transformation risks. Polypharmacy, DDIs, and PIMs are very frequent among MPN patients and may have important clinical associations.


Introduction
Philadelphia chromosome-negative myeloproliferative neoplasms (MPNs), essential thrombocythemia (ET), polycythemia vera (PV), and myelofibrosis (MF), share several clinical and biological characteristics; these include the overproduction of erythroid, megakaryocytic and granulocytic cells, frequent splenomegaly, variable degrees of bone marrow fibrosis, and an increased thrombohemorrhagic risk [1,2]. The majority of MPN patients bear mutually exclusive driver mutations in the Janus kinase 2 (JAK2) [3,4] or calreticulin (CALR) genes [5,6] that constitutively activate the JAK-STAT signaling pathway which causes excessive myeloproliferation and a persistent chronic inflammatory state response responsible for the frequent constitutional symptoms associated with the disease [7,8]. Life expectancy in ET and PV is worse than in the general population, mainly due to adverse cardiovascular (CV) events and disease transformation to secondary MF (SMF), myelodysplastic syndrome (MDS), or acute myeloid leukemia (AML) [9,10]. The median

Study Design and Patient Population
This was a single-center study conducted at the General Hospital of Sibenik-Knin County, Sibenik, Croatia in the period between January 1996 and November 2022. Patients with MPNs were retrospectively identified through medical chart review and the details regarding demographic, clinical, and laboratory data were collected at the time of disease diagnosis or at the time of first patient referral. ET, PV, and MF disease diagnoses were first extracted from the medical records using the International Classification of Diseases (ICD), 10th revision, codes for MPNs (D45.0, D47.1, D47.4, D75.2, C94.5) which were then manually verified and reassessed according to World Health Organization (WHO) 2016 criteria [34]. For patients diagnosed before 2005 (when the JAK2-V617F mutation was first discovered), this mutation analysis was performed patients when it became available. CALR mutations were performed in a smaller proportion of ET and MF patients after it became available in Croatia (2016). Patients lost to follow-up or with missing data were excluded. The study flowchart is presented in Figure 1. Disease-related symptoms were defined as fatigue, night sweats, weight loss (>10% of body weight in the preceding 6 months), fevers, pruritus, lack of concentration, headaches, and early satiety. Cardiovascular risk factors of interest were arterial hypertension (defined as arterial blood pressure >140/90 mmHg or the use of antihypertensives), hyperlipidemia (total cholesterol >5 mmol/L and/or low-density lipoprotein levels >3 mmol/L or the use of antilipemics), diabetes mellitus (diagnosed by an endocrinologist), smoking (active/prior vs. never smoker) and chronic kidney disease (estimated glomerular filtration rate < 60 mL/min/1.73 m 2 ≥ 3 months). Chronic heart failure (CHF) was defined as left ventricular ejection fraction < 50% or the need for diuretics to keep euvolemia. Hyperuricemia was defined as serum uric acid >428.26 µmol/L for adult males and >356.88 µmol/L for adult females [35].
A total number of prescriptions was determined for the entire follow-up. We used Anatomical Therapeutic Chemical Classification (ATC) system developed by the WHO to stratify medications into 14 categories according to their therapeutical and chemical characteristics (URL: http://www.whocc.no/atc/structure_and_principles/; accessed on 10 February 2023). Polypharmacy, PIM, and DDI were defined at study entry, and patients stratified as such did not change their status during the study follow-up. Polypharmacy marked the concomitant use of ≥5 medicines and PIMs were classified according to EU(7)-PIM list; the latter tool is recommended to screen for medications in elderly persons (>60 years of age) which should be avoided due to a high risk of adverse events and/or insufficient evidence of their benefit and when there are equally or more effective but lower risk alternatives available [36]. DDIs were stratified using Lexicomp ® (Lexi-Drug Interaction Online; UpToDate, Inc.: Hudson, OH, USA) [37]. This online software classifies DDI into five categories; A (no interaction), B (no action needed), C (monitor therapy), D (modify regimen), and X (avoid combination). Considering the generally harmless nature of A and B interactions and for the purpose of this analysis, we focused solely on C, D, and X interactions.

Statistics
According to Shapiro-Wilk's test, the data were not normally distributed so we used nonparametric statistical tests. Categorical variables were compared with the chi-square test and continuous variables were analyzed with the Mann-Whitney U test. Overall survival (OS) was calculated as the time from diagnosis until death or the last follow-up visit. Time to thrombosis (TTT) was measured as the time from diagnosis until the first thrombotic (arterial or venous) event with patients being censored at the time of last followup or death, whereas time to bleeding (TTB) was measured as the time from diagnosis until the first bleeding event. Thrombotic and bleeding events present before or at the time of disease diagnosis were not taken into account for TTT and TTB calculation. Time to disease transformation (TDT) was measured as the time from disease diagnosis until the time of transformation to SMF, MDS, or AML. Survival analyses were performed with the Kaplan-Meier and the Cox regression analyses. Arterial thrombotic events considered were acute myocardial infarction, transitory ischemic attack, acute ischemic stroke, and acute peripheral arterial occlusion, whereas venous thrombotic events were defined as deep vein thrombosis and/or pulmonary embolism. Statistical calculations were performed with MedCalc Statistical Software (Medcalc Software Ltd., Ostend, Belgium, version 20.216).
A total of 66 PIMs were identified; the most frequent PIMs were prolonged proton pump inhibitor (n = 15, 22.7%), tramadol (n = 11, 16.6%), and diazepam (n = 6, 9.1%) use. There was a total of 306 C interactions and the most commonly encountered were the combination of antihypertensives and loop diuretics (n = 43, 14%), followed by concomitant use of angiotensin-converting enzyme inhibitors (ACE-i), thiazides, and thiazide-like diuretics (n = 23, 7.5%), and the simultaneous use of ACE-i and salicylates (n = 21, 6.8%). A total of 32 D interactions were recorded; the most frequent ones were the concomitant use of warfarin and allopurinol (n = 5, 15.6%), combinations of opioids and central nervous system depressants (n = 5, 15.6%), and the simultaneous use of hydroxyurea and denosumab (n = 3, 9.3%). A complete list of PIMs and DDIs found in our MPN cohort with detailed explanations regarding their potential adverse health effects and pharmacodynamic DDI are provided in Tables 1 and 2.
Iron supplements > 325 mg 2 (3%) Doses > 325 mg/day do not considerably increase the amount absorbed but greatly increase the incidence of constipation.     The median number of PIMs, C, and D interactions was 0 (range 0-4), 3 (range 1-20), and 1 (range 1-4), respectively. There were no statistically significant differences in the number of prescribed medications (p = 0.338), prevalences of polypharmacy (p = 0.250), PIMs (p = 0.857), and DDIs (p = 0.228) in ET vs. PV patients; we did not test for differences in MF and MPN-unclassified due to the small number of patients included. Both PIM (p < 0.001) and DDI (p < 0.001) correlated with the presence of polypharmacy.
As shown in Table 3., polypharmacy was associated with older age, prior thrombosis, presence of disease-related symptoms, oral anticoagulants, osteoarthritis/osteoporosis, autoimmune disorders, less frequent splenomegaly, and medications used for the management of CV diseases (atrial fibrillation, CHF, arterial hypertension, and hyperlipidemia). Similarly, DDI was also associated with older age, oral anticoagulants, osteoarthritis/osteoporosis, and CV disorders, whereas the use of PIMs was more frequent in patients with prior arterial thrombosis, those treated for psychiatric disorders and liver cirrhosis, and in patients using oral anticoagulants and proton pump inhibitors (p < 0.050 for all analyses). Finally, MPN patients with higher hemoglobin and hematocrit levels more often had D interactions; these may be caused by increased myeloproliferation and a higher disease burden and account for more frequent allopurinol, analgetic and anxiolytic use.
Univariately, median OS was significantly shorter in an overall cohort of ET and PV patients using polypharmacy (median 157 vs. 258 months, hazard ratio-HR 2.80, p = 0.002) and with DDIs (median 159 vs. 258 months, HR 2.00, p = 0.035), whereas PIMs did not affect OS (p = 0.535), as shown in Figure 2. The associations of DDI with an inferior OS persisted for both C (HR 2.00, p = 0.036) and D interactions (HR 2.77, p = 0.067). Both polypharmacy (HR 5.22, p = 0.022) and DDI (HR 4.88, p = 0.027) remained independently associated with an inferior OS in the multivariate Cox regression models additionally adjusted for sex, high-risk disease, presence of CV risk factors, baseline leukocytosis, and cytoreductive treatment, as shown in Supplementary Table S3.
Median TTT was significantly shorter in patients using polypharmacy (median 163 months vs. not reached, HR 3.28, p = 0.012) and with DDI (median 182 months vs. not reached, HR 2.50, p = 0.042) whereas there were no statistically significant differences in TTT with respect to PIM (p = 0.151), as shown in Figure 3. When analyzed separately, the association of DDD with an inferior TTT was significant for C interactions (HR 2.56, p = 0.036) but not for D interactions (p = 0.498) which could be due to a smaller number of D interactions present in the study population. In the multivariate Cox regression models adjusted for sex, high-risk disease, presence of CV risk factors, JAK2 mutation, baseline leukocytosis, and cytoreductive treatment, polypharmacy (HR 7.60, p = 0.008) and DDIs (HR 5.00, p = 0.025) remained as predictors of an inferior TTT, as presented in Supplementary Table S4.  There were no significant associations of polypharmacy, PIM, and DDI with respect to TTB (Supplementary Figure S1) and TDT (Supplementary Figure S2).
Finally, we would like to point out that these survival analyses should be considered hypothesis-generating considering the absence of validation in an independent cohort.

Discussion
To our knowledge, this is the first study to provide comprehensive details regarding the medication use in MPNs and the frequencies of polypharmacy, PIMs, and DDIs in this specific patient population. We showed that polypharmacy (61.3%), PIM (45.5%), and DDI (62.1%) are very frequent among MPN patients. In fact, polypharmacy seems to be significantly higher than in the general population (39% in persons ≥65 years of age) [26] and, together with DDI, is mostly associated with the management of disease-related symptoms in MPNs, osteoarthritis/osteoporosis, and different CV disorders, i.e., atrial fibrillation, CHF, arterial hypertension, hyperuricemia, or hyperlipidemia. These observations again highlight the significant symptom burden and the importance of appropriate CV risk management in MPN patients.
The most common PIM was prolonged proton pump inhibitor use-this may be related to the fact that MPN patients have been shown to frequently suffer from dyspepsia, Helicobacter pylori infection, and peptic ulcer disease [38,39]. Considering that PIM also correlated with the presence of prior thrombosis and anticoagulant use, this could suggest that many MPN patients receive prolonged proton pump inhibitor treatment together with aspirin and/or oral anticoagulants due to already present dyspeptic symptoms and/or because of physicians' fear of future adverse gastrointestinal events. These observations may be even more important in the light of recent evidence suggesting suboptimal platelet inhibition in ET with once-daily low-dose aspirin when compared to more intensive aspirin regimens which may also cause more abdominal discomfort [40]. On the other hand, even though prolonged pump inhibitors were the most common PIM, none of the MPN patients experienced Clostridium difficile infection. Other common PIMs were tramadol and diazepam. It should be pointed out that many MPN patients suffer from anxiety and depression [41], warranting the use of anxiolytics. On the other hand, osteoarthritis [42] and osteoporosis [43] have been shown to be a frequent feature in MPNs, and tramadol and/or nonsteroidal anti-inflammatory drugs used for their treatment could be involved in a significant proportion of PIMs and DDIs. Specifically, tramadol and diazepam may cause synergistic depressive effects on the central nervous system and be responsible for adverse health outcomes. In addition, we found that diazepam and other anxiolytics were often chronically used by MPN patients which is not standard practice due to their addictive effect. This suggests that many MPN patients may indeed suffer from different cumbersome disease-related symptoms (i.e., itching, anxiety, or insomnia) warranting such treatment for symptom relief. Finally, the use of PIMs was not associated with inferior outcomes in MPNs, possibly due to the fact that proton pump inhibitors were the most common PIMs, and these compounds are usually considered to be relatively safe medications.
Even though there are no guidelines to suggest its use in MPN patients, allopurinol was frequently prescribed to MPN patients and its interactions with warfarin and loop diuretics were often found. Allopurinol is a drug often used in MPN patients due to baseline hyperuricemia or because of fear of anticipated hyperuricemia caused by an increased cell turnover during cytoreductive treatment. More importantly, hyperuricemia was also recently shown to be associated with inferior outcomes MPNs [16,17]. Therefore, considering that a significant proportion of MPN patients may suffer from thrombotic events, arterial hypertension, or CHF, necessitating the use of warfarin or diuretics, future studies are warranted to fully elucidate the role of serum uric acid in the pathogenesis of thrombosis in MPNs and whether the use of allopurinol may have a beneficial effect on different disease-related outcomes. This may be even more important when considering the allopurinol-related DDIs and the fact that the vast majority of MPN patients do not have gout and have well-controlled serum uric acid levels, thus questioning the role of continuous allopurinol use. Other common DDIs were the combinations of ACE-i and diuretics, or the simultaneous use of ACE-and salicylates, potentially having synergistic hypotensive and nephrotoxic effects, respectively. In addition to their negative effects on the CV system due to synergistic hypotensive properties, these DDI may also cause worsening of kidney function which has been associated with inferior outcomes in MPNs [18][19][20]. On the other hand, the use of ACE-i has been shown to have renoprotective properties in PV [44], suggesting that the hypotensive CV effects could be the more detrimental ones.
The adverse health effects of polypharmacy and DDI were also confirmed in survival analyses. Both polypharmacy and DDI were shown to be predictors of an inferior OS, independently of high-risk disease and the presence of CV risk factors. This important observation suggests that inadvertent DDI due to multiple medication use may be responsible for the inferior outcomes in a subset of MPN patients. Moreover, both polypharmacy and DDI predicted an inferior TTT rendering other clinically relevant risk factors insignificant during multivariate analyses, most probably due to their overlapping prognostic properties. Nevertheless, these results may provide an important danger signal regarding the potential risks of combining drugs with pharmacodynamic interactions in MPN patients.
Even though combinations of warfarin-allopurinol and aspirin-salicylates DDI were frequently encountered in our MPN cohort and the fact that their pharmacodynamic synergism may potentially cause an increased risk of bleeding, we did not observe such associations. This may be because MPN patients are more prone to thrombosis than the general population, countering the potentially negative effect of these interactions. In addition, the presented cohort had a very low number of CALR-mutated patients whose thrombotic risk is much lower than that of their JAK2-mutated counterparts [1]. No effect of polypharmacy, PIM use, and DDI was seen regarding the disease transformation risk. It is noteworthy that hydroxyurea, a cytoreductive medication most often used to treat MPNs in this patient cohort, does not have a large number of clinically significant DDI [37]. Even though disease-modifying properties and thus attractiveness of the use of hydroxyurea and other cytoreductive drugs are still debated, the absence of significant DDI may provide further reassurance to physicians regarding its safety and efficacy in the treatment of MPNs.
The limitations of this study are its retrospective single-center design and the limited number of patients included. Additionally, due to the small number of MF patients, we could only assess the prognostic impact of polypharmacy, PIM, and DDI in ET and PV patients. Therefore, future studies should focus also on MF patients. Nevertheless, this study provided important signals regarding the potential risks of polypharmacy and DDI in MPN patients and it may alert the clinicians caring for MPNs to stay vigilant and tactful in managing disease-related symptoms and to periodically reassess medications used to treat patients' other clinical conditions, especially CV disorders. Shared decision-making by physicians and MPN patients should be implemented in order to avoid medication overuse and potentially inadvertent DDI.
Supplementary Materials: The following supporting information can be downloaded at: https://www. mdpi.com/article/10.3390/biomedicines11051301/s1, Table S1: Total number of drug precriptions; Table  S2; Total number of prescribed medications according to Anatomical Therapeutic Chemical Classification (ATC) system; Table S3: Multivariate Cox regression analysis of factors associated with overall survival. DDI = drug to drug interactions, CV = cardiovascular, PV = polycythemia vera, HR = hazard ratio; Table  S4: Multivariate Cox regression analysis of factors associated with time to thrombosis. DDI = drug to drug interactions, CV = cardiovascular, JAK2 = Janus Kinase 2, HR = hazard ratio; Figure S1: Time to bleeding (TTB) in essential thrombocythemia (ET) and polycythemia vera (PV) patients according to polypharmacy (A), potentially inappropriate medications-PIM (B) and drug-to-drug interactions (C). The Kaplan-Meier and the log-rank tests were used; Figure S2: Time to disease transformation (TDT) in essential thrombocythemia (ET) and polycythemia vera (PV) patients according to polypharmacy (A), potentially inappropriate medications-PIM (B) and drug-to-drug interactions (C). The Kaplan-Meier and the log-rank tests were used.